Method and apparatus for removing counterbore plugs



Aug. 2, 1966 E. R. EWASKOWITZ METHOD AND APPARATUS FOR REMOVING COUNTERBORE PLUGS Filed Oct. 18, 1963 United States Patent 3,263,721 METHOD AND APPARATUS FOR REMOVING COUNTERBORE PLUGS Eugene R. Ewaskowitz, 435 N. Hudson St., Sturgeon Bay, Wis.

Filed Oct. 18, 1963, Ser. No. 317,360 2 Claims. (Cl. 144310) This invention relates to improvements in wood drilling bits and methods especially adapted for removing plugs which have previously been secured in counterbored new plug may be installed later to restore the previous appearance of the area. This is never easy, because these plugs are tightly held by glue or other adhesive. It

should further be possible to extract the screw itself without damaging the margins of the counterbore. The operation of digging of the adhesive out of the kerf or other slot of a screw, always necessary before a screw driver may be employed, has often resulted in damage .to the margins of the counterbore.

Heretofore, plugs have been removed from counterbores principally by laborious chipping and digging them out with wood chisels. Damage to the margins of the counterbores could be expected from such methods and frequently occurred.

Often, a single repair or remodeling job on a boat requires the removal of 300 to 500 and more wooden plugs. When this is done in areas which are normally varnished and polished to attain and preserve a piano finish, plug removal alone accounts for an enormous cost in time and wages. Obviously, a power-driven tool should i be used in place of Chisels to save time, but no satisfactory wood bit suitable for power operation has been available heretofore. i

It is the broad objective of this invention to provide a new method and a new tool for removing counterbore plugs more neatly and efliciently than has heretofore been possible.

Another objective is .to provide a new method for the above purpose, which entirely eliminates the use of a chisel and which is speedier than any method'heretofore employed in this task.

Another objective is to provide a wood bit which, while attached to an electric drill, can be guided easily and i accurately in the process of perfectly drilling out a cylindrical counterbore.

Another objective is to provide a bit which will remove all of the plug down to the top surface of the wood screw, and, at the same time without special manipulation, remove glue or other foreign matter from the center of the diametrical kerf in conventional woodscrews or from the central tool socketof such screws as Phillips screws and Reed and Prince screws.

Another objective is to provide a Wood bit for the foregoing purposes which, without damage to itself, and

foregoing purpose which enables an operator to drill out the plugs more perfectly and in a-small fraction of the time required by heretofore known and less perfect means and methods.

Other objectives and advantages of the invention will be mentioned hereinafter, or will become apparent in the following specification.

Referring now to the drawings, FIG. 1 is a plan view of a inch drill bit, shown atdouble its actual size.

FIG. 2 is a side elevation of the same bit, on the same scale.

FIG. 3 is an end elevation of the same bit, at four times its actual size.

FIG. 4 is an end view of the end of the bit, as positioned in FIG. 2, and at eight times its actual size.

FIG. 5 is a view in section of a wood structure having a counterbore therein containing a natural wood plug, a crossslotted Reed and Prince flat head screw, and a bit poised for entering the plug.

FIG. 6 is a view showing the bit after it has drilled out the plug and showing a projection on the bit entered into the slot of the screw.

FIG. 7 shows a screw driver after it has been inserted into the slot of the screw, displacing some of the glue which the slot had previously contained.

FIG. 8 is a perspective view of the same drill at abou double its actual size and carrying thereon an adjustable collar. i

FIG. 9 is a plan view of the head of a typical flat head Reed and Prince screw.

Referring further to the drawing, the bit includes preferably a shank 11 for attachment to a hand brace or to an electric drill. Preferably integral with the shank is a blade-like drill generally indicated as 12, whose width extends diametrically of the plug to be drilled. Preferably, the blade width should be slightly less than the plug or counterbore diameter, usually about of an inch less. The blade is preferably substantially flat to provide opposed wide faces 33 and 34 connected by narrow faces or sides 13 and 14.

Preferably, .as shown in FIG. 2, the thickness of the blade is only a small fraction ofthe width of the blade,

and the opposite longitudinal sides 13 and 14 are bevelled back from their leading edges, referring to the normal direction of rotation, to provide'suitable clearance in the counterbore. While these leading edges, lengthwise of the blade, may be sharp, they are not intended to function normally as cutting edges.

As seen in FIGS. 1 and 4, the blade has a free end margin comprising the portions 15 and 16 which are used ascutting edges for drilling out the plug. These portions should be bevelled by grinding or filing, to sharpen the leading edges in the normal direction of rotation, the degree of bevel found to be most elficient is shown in FIG. 4.

Extending centrally from the free end margin of blade is a specially designed and shaped projection 17, of a length approximating the'thickness ofthe blade having sides 18 and 19 which taper inwardly from approximately the planes of the faces 33 and 34, beginning at the end margin merging at a sharpened edge intermediate and substantially parallel to faces 33 and 34 of the blade 12.

when completely drilling out a plug, may be and is in- This projection is not a ,lead point or pilot point as isoftenfound in wood bits. It does not draw the bit into the plug, nor does it have much if any value for centering the drill; In fact, its centering ability is so slight that the operator, if not working on a plug, could move a drill having this projection, while it isengaged with the surface of a board quite readily sidewise along-that surface, cutting a groove therein the depth of the projection. When the operator is beginning to drill out a plug,

-he centers the tool by eye as closely as possible when engaging the projection 17. As the cutting edge approaches not exceed about three and one-half inches.

the plug 20, if the bit is not aligned accurately he aligns it by merely guiding it with the fingers of one hand resting on the adjoining surface.

The primary function of the projection 17 is eventually to cause it to enter into the kerf or other tool receiving slot with which the covered screw is equipped and to chip out or displace whatever glue or other matter it encounters, thus facilitating the subsequent introduction of a screw driver into that slot. In the case of a Reed and Prince screw slot or similar slot, a substantial amount of the glue may thus be removed. If the slot is a conventional diametrical kerf, enough of the glue is removed "so that the operator can find the direction in which the kerf lies and tap or otherwise force a screw driver blade thereinto.

The full entrance of the projection 17 into a center 21 of the intersecting slots 22 and 23 of a Reed and Prince wood screw 24 is illustrated in FIG. 6. It will be observed that the plug has been drilled out completely to the now exposed surface of the head of the screw. A Reed and Prince fiat head screw is illustrated, because it is very commonly used in boat construction.

In order to obtain the full advantages of the projection 17 in removing as much of the glue or other matter as is possible from the center of a screw slot, the width of the projection at its juncture with the blade, which may be termed the base of the projection, should approach as closely as is possible to the size of the central opening into the slot without, however, engaging the margins of the slot. The length of projection 17 should not exceed the depth of the slot.

The collar 25 may be slotted to fit snugly upon the blade, as shown in FIG. 8, and clamped thereon by a set screw, preferably an Allen set screw 26. It is employed when. the bit is used as a counterboring tool, and in such powered hand drill for drilling out plugs which cover and conceal screws seated in the bottoms of counterbores, which usually are substantially less than an inch in depth. It is preferred that the total length of the shank and blade Using such a short assembly of shank and drill blade protruding from the chuck, the operator may rest one hand on the surface and, with the fingers of that hand, guide the tool to cause it to register accurately with the plug circumference when entering the plug and to remain centered in the counterbore.

When the motor driven drill has removed all of the plug, as seen in FIG. 6, the projection 17 will have entered the center 21 of the cross slots and will expel the glue usually to be found there. As this stage in the operation is reached, the operator. will note that the end of the drill is lightly contacting the face 7 of the screw.

He may then withdraw the drill and insert the end of a manual screw driver 27 into the counterbore. The point will enter the center from which glue has been removed and the operator can readily ascertain the position in which the cross slots lie and rotate the radial vanes of the screw driver to register with the slots. He then should give the screw driver a sharp blow with a hammer. This will expel all or enough glue from the slots to permit use of a power driven screw driver for unscrewing the screw. FIG. 7 indicates at 28 and 29 glue which has been displaced from the slots. By employing the herein described method of plug and screw removal, as compared with the prior use of chisels, an operator can remove a large number of plugs and screws per hour, rather than just a few.

As the projection 17 is not relied on as a centering point for this drill, it is recommended that the operator rely on his own hands for holding the drill centered as it moves into the counterbore.

Whenever the end margins 15 and 16 become d-ull, a satisfactory sharpening method requires only the use of two opposed parallel faces 31 and 32 of the projection are perpendicular to the planes of the broad flat sides 33 and 34 of the blade 12, hence the motion of a flat file being parallel to faces 31 and 32 leaves the thickness of the projection between those faces undisturbed. Whenever, the projection 17 becomes too long, as a result of filing of the adjoining end margins of the blade, the projection itself may be shortened by filing.

This convenience, which attends the sharpening of the cutting edges 15 and 16 without widening the base of projection 17, would not prevail if the two sides 31 and 32 were tapered to meet at a sharp line edge and the other two sides of the projection were extended in the plane of the bit faces 33 and 34.

As may be noted in FIG. 4, the angle of the bevel at which the cutting edges 15 and 16 are filed or ground is indicated at 5, an angle which is much preferred over any other angle, as it appears to promote the highest efficiency of the bit in drilling out counterbore plugs. Since all of the drilling out or cutting of the plug is done by the two edge portions 15 and 16, it is important that they retain the maximum lateral lengths possible, consistent with the presence of projection 17 and its important function, and that they be as efficient cutters as is possible.

The same angle of 5 is also preferred for the longitudinal sides 13 and 14 of the blade bit (FIG. 5), as this angle assures a free running clearance in the counterbore and, under the circumstances of usual careful operation, little tendency of the sides of the bit to cut into the counterbore and disturb its original smooth cylindrical internal surface.

While a preferred embodiment of the invention is shown herein, it should be understood that the invention is not limited to the details of that embodiment, but embraces such variations and modifications as fall within the scope of the claims appended here-to.

I claim:

1. The method of removing a recessed slotted wood screw and superimposed plug from a counterbore of a wood structure with a blade type drill bit having a blade width slightly less than the diameter of the counterbore, a cutting end perpendicular to the bit axis and a central projection having a transverse dimension for entry in the screw slot and a length less than the depth of the screw slot, said method comprising, placing the point of the rotating bit against the plug at the estimated center of the plug to form a shallow depression in the plug, drifting the point of the bit laterally as the cutting end approaches the plug to center the cutting end of the bit on the plug, aligning the axis of the blade with the axis of the plug, moving the blade and projection inwardly through the plug to remove the same, continuing said inward movement of the blade until the cutting end lightly engages the head of the screw to bring the projection into the screw slot and remove solid material from the slot in response to rotation of the bit, subsequently radially ejecting additional solid material from the slot to condition the same for the reception of a screw driver and thereafter removing the screw with a screw driver.

2. A wood drill bit for drilling out a plug and removing associated material from a counterbore having a slotted wood screw seated beneath the plug comprising a shank for attachment to a driving unit, a blade having a width in the region of inch less than the diameter of a preselected conventional counterbore tool and having a generally rectangular cross section transversely of its length, said blade being thin relatively to its width and extending from one end of the shank, the free end margin of said blade being perpendicular to the blade length, a relatively small projection extending from the center of said margin, said projection having a sharp point and having a maximum transverse dimension at its juncture with said margin approaching 'but not exceeding the minimum Width of the entrance to the slot in a preselected size of conventional wood screw head, the projection having a length approaching but not exceeding the depth of said slot and having two opposed flat uninterrupted sides mutually parallel and extending perpendicular to the width of the bit blade and two other sides tapered substantially throughout their length to and merging at a sharpened edge, said blade margin at each side of said projection being shaped and sharpened to provide two cutting edges perpendicular to the blade length.

References Cited by the Examiner UNITED STATES PATENTS Fancher 20-93 Rosan 29-426 Smith 145-116- Hoover 14550.1 Robinson 145-116 Joyce 14550.1

HAROLD D. WHITEHEAD, Primary Examiner.

WILLIAM W. DYER, IR., Examiner. 

1. THE METHOD OF REMOVING A RECESSED SLOTTED WOOD SCREW AND SUPERIMPOSED PLUG FROM A COUNTERBORE OF A WOOD STRUCTURE WITH A BLADE TYPE DRILL BIT HAVING A BLADE WIDTH SLIGHTLY LESS THAN THE DIAMETER OF THE COUNTERBORE, A CUTTING END PERPENDICULAR TO THE BIT AXIS AND A CENTRAL PROJECTION HAVING A TRANSVERSE DIMENSION FOR ENTRY IN THE SCREW SLOT AND A LENGTH LESS THAN THE DEPTH OF THE SCREW SLOT, SAID METHOD COMPRISING, PLACING THE POINT OF THE ROTATING BIT AGAINST THE PLUG AT THE ESTIMATED CENTER OF THE PLUG TO FORM A SHALLOW DEPRESSION IN THE PLUG, DRIFTING THE POINT OF THE BIT LATERALLY AS THE CUTTING END APPROACHES THE PLUG TO CENTER THE CUTTING END OF THE BIT ON THE PLUG, ALIGNING THE AXIS OF THE BLADE WITH THE AXIS OF THE PLUG, MOVING THE BLADE AND PROJECTION INWARDLY THROUGH THE 